Mixed Substitution in P-Doped Anatase TiO2 Probed by XPS and DFT

Abstract

The investigation of the electronic structure of P-ion implanted TiO2 thin films (E=30keV, D=1x10(17)cm(-2)) with anatase structure is performed by X-ray photoelectron spectroscopy (XPS) measurements (core levels and valence bands) and first-principles density functional theory (DFT) calculations. It is found that the XPS P 2p-spectra reveal the presence of two signals at 134.2 and 130.3eV which can be attributed to the formation of P-O (with P5+ ions) and P-Ti (with P3- ions) bonds, respectively. This means that both cationic (PTi) and anionic (PO) substitution take place in P-ion implanted anatase thin films. This conclusion is confirmed by DFT calculations which show that the XPS valence band structure of P:TiO2 can be reproduced only under mixed substitution. The presence of two kinds of phosphorus ions (P5+ and P3-) in ion-implanted TiO2 can be useful for developing new multifunctional advanced materials with configurable properties for a wide range of applications.